Venous filter for assisted venous return

Abstract

The need for a venous reservoir in a heart-lung machine is obviated by using a vacuum-purged negative-pressure air filter in the venous return line ahead of the main blood pump. The purging vacuum for the venous air filter can also be used to purge air from the cardiotomy reservoir if a backflow-preventing valve is used on the venous air filter.

What is claimed is:  
     
       1. A heart-lung machine, comprising: 
       a) a venous return line receiving venous blood from a patient, said venous return line being under negative pressure;  
       b) an arterial supply line supplying arterial blood to the patient;  
       c) a negative pressure air filter connected directly to said venous return line so as to draw the patient's venous blood through said negative pressure air filter;  
       d) a blood pump and a blood oxygenator connected between said negative pressure air filter and said arterial supply line, said blood pump being arranged to pump blood directly from said negative pressure air filter toward said arterial supply line; and  
       e) said negative pressure air filter including:  
       i) a blood intake;  
       ii) a bubble trap arranged to trap air bubbles present in the patient's venous blood;  
       iii) an air chamber positioned above said blood intake and arranged to receive air bubbles trapped by said bubble trap;  
       iv) an air sensor arranged to sense the presence of air in said air chamber; and  
       v) a vacuum applied to said air chamber, said vacuum being applied when, and only when, said sensor senses the presence of air In said chambers so as to maintain said filter filled with blood but prevent blood from being aspirated into a purge line.  
     
     
       2. The heart-lung machine of claim  1 , further comprising: 
       f) a suction pump arranged to draw cardiotomy blood from said patient;  
       g) a cardiotomy reservoir containing a cardiotomy filter arranged to receive said cardiotomy blood, filter particulates and air therefrom, and convey filtered blood to said blood pump, said cardiotomy reservoir having an air chamber to receive the air filtered from the cardiotomy blood; and  
       h) a vacuum source connected to said air chamber of said cardiotomy reservoir.  
     
     
       3. The heart-lung machine of claim  2 , in which said vacuum source provides a vacuum to both said cardiotomy reservoir and said negative-pressure air filter, and in which a check valve is further so connected to said negative pressure filter to prevent the negative pressure in said negative pressure filter from drawing cardiotomy blood into said negative pressure filter when said vacuum is turned off. 
     
     
       4. A negative pressure venous air filter, comprising: 
       a) an airtight container;  
       b) a blood inlet on said container is adapted to be connected to a venous return line for introducing venous blood into said container;  
       c) a blood outlet on said container directly connected to a source of negative pressure for pumping venous blood out of said container;  
       d) an air chamber in said container above said blood inlet  
       e) a bubble trap in said container for entrapping air in said venous blood and conveying it to said air chamber; and  
       f) a vacuum connection at said air chamber connecting said air chamber to a vacuum source for evacuating said air chamber so as to maintain said container filled with blood;  
       g) wherein a suction force created by said vacuum source is greater than said negative pressure.  
     
     
       5. The air filter of claim  4 , in which said connection connecting said air chamber to said vacuum source is a purge line of substantially 6 mm inner diameter. 
     
     
       6. The air filter of claim  5 , further comprising a check valve in said purge line for preventing fluid flow from said purge line into said air chamber. 
     
     
       7. The air filter of claim  4 , further comprising: 
       h) an air sensor arranged to sense the pressure of air in said chamber, and to activate said vacuum source when and only when air is present in said chamber.